Leather-stretching machine.



P. 0. BROWN LEATHER STRETCHING MACHINE.

APPLICATION FILED OCT. 7, 1916.

Patented Apr. 8, 1919.

3 SHEETSSHEET I 1 .n. 1 TL.

P. 0. BROWN.

LEATHER STRETCHEING MACHINE.

APPLICATION FILED OCT. 7. 1916.

Patented Apr. 8, 1919.

3 SHEETS-SHEET 2.

P. 0. BROWN.

LEATHER STRETCHNG MACHINE APPLICATION FILED OCT. 1, 191a.

Patented Apr. 8, 1919.

3 SHEETS-SHEET 3.

Fig.1

Z x/W PHILIP CARTER BROWN, 01-? DOVER, NEW HAMPSHIRE.

LEATHER-STRETCHING MACHINE.

Specification of Letters Patent.

Patented Apr. 8, 1919.

Application filed October 7, 1916. Serial No. 124,436.

To all whom it may concern:

Be it known that .I, PHILIP CARTER BROWN, a citizen of the United States, residin at Dover, in the county of Straflord and tate of New Hampshire, have invented certain new and useful Improvements in Leather- Stretching Machines, of which the following is a specification.

My invention relates to leather stretching machines, 6. e., to machines for stretching skins, hides, or pieces of leather, especially such pieces as are to be used'for making belting. My invention relates more particularly to machines" of this general type in which opposite ends of the leather are gripped by clamping devices or clamps which are spaced apart and adapted to be relatively drawn awayfrom one another so as to put the leather under tension. Each clamp commonly comprises an upper jaw and a lower jaw and is provided with'means for bringing the jaws forcibly together upon the leather so as to'hold thesamewithout slip.

In the prior art, machines of this kind have been. provided with clamp members or jaws of cast iron, the opposed faces thereof being formed, respectively, as a single convex and concave surface (the two faces be- 'ing, hence, complementary to one another) so as to insure a good grip upon the leather.

. In somecases the clamp members, instead of having complementary curved surfaces, have been formed with V-shaped teeth, each jaw havingsometimes one and sometimes a plurality of teeth. Where a plurality of ii-shaped teeth have been employed, however, the distancefrom tooth to tooth has been substantially less than the thicknessof the leather to be stretched. In still other cases, no attempt has been made to provide special gripping surfaces for the clamp members but various special and independent holding devices have been inserted between each clamp member and the leather.

Where jaws having'plane or simple curved surfaces have been used, it has been impossible to hold the leather securely except by giving the jaws a very considerable width. Since that portion of the leather lying between .the jaws has not ordinarily been stretched, it must be cut from the stretched portion and is therefore waste for which some special use must be found if it is to have any value. Where-the jaws are provided with \l-shaped teeth, the jaws may, indeed, be made narrower but that portion of the leather between the jaws becomes so gashed' and'mutilated by the sharp edges of the teeth that it is rendered valueless for any practical purposes. And in the case where special holding devices are utilized between the clamp members, an undue amount of time is required in adjusting the devices in position with respect to the clamps and the leather. I

Another grave disadvantage attendant upon clamp members such as have been described, is the fact that the leather in contact with the clamps will be discolored or blackened, due probably to chemical action between the iron and organic materials in the leather; or to chemical action between the iron and materials incorporated in the leather during the tanning and preliminary treating process. This blackening or discoloration tends to be aggravated by reason of the currying grease and water forced from the leather by the pressure of the clamps, which materials will also be blackened and will spread over other regions of the leather so as to blacken and damage them as well. This blackening obviously greatly depreciates the value and salabilityof the leather wherever it occurs.

In the case of any of the previously known types of clamp above referred to, the greases forced from the leather by the clamping creased width of clamp or a more pro- I nounced tooth surface, and hence accentuates the disadvantages already referred to. One object of my herein about to be descreibed invention is to provide clamp members having faces or clamplng surfaces of special shape such that they may be quite forming its surface. Still another object of my invention is to provideam-aterieli for the clamping members, or for the faces of said clamp ng members, which shal not ie-M chemically, or otherwise, with materials contained in the leather so as to blacken -or dis= color the same and which at the same time is so hard and: unyielding that it can be embodied in very narrow clamps of small crosssection to which very great pressures may be applied without danger of deforming the clamps, whereby the leather may be very securely held,

Briefly described, my invention resides in providing clamping members for leather stretching machines having opposed complementary and interlocking faces, each of these faces comprising a plurality of smoothly curved flutes, as distinguished from teeth. The clamp members, or those portions of the clamp members which include the fluted faces, are made of nickelbronze, preferablyby the extrusion process, which material I have found will not stain or discolor the leather.

My invention will'be better understood by referring to the accompanying-drawings in which Figure 1' represents aside elevation of a conventional leather stretching machine having my invention embodied therein; Fig. 2 represents a top plan view of the machine shown in Fig. 1; Fig. 3 represents a top plan View, on a scale twice-that of Figs. 1 and 2, showing the stretcher and the two stretching clamps; Fig. 4' represents the view shown in Fig. 8 in side elevation; Fig. 5 represents an elevation, part section, twice enlarged, taken from the left of Fig. 3;-Fig. 6 is a view, similar to Fig. 5, taken from the left of line 66 of Fig. 3,; Fig. 7' represents a section taken along the line 7'7 of Fig. 6;'Fig. 8 represents a; section, similar to Fig. 7, taken along the line 8-8 of Fig. 5; Fig. 9' represents an end View taken from the right of Fig. 1 Fig. lOrepresents, on an enlarged scale, a side elevation of the hanger attached to the inner end of the stretcher; Fig. 11 is a section, twice enlarged, taken along the line 1111 of Fig. 2; Fig. 12 represents, enlarged, a transverse section through a preferrediform of-one of my improved clamp members, the same being shown in the sev eral drawings as a. removable insert; and Fig.- 13: shows, on" a. greatly enlarged scale,

the shape of the recurring pair of flutes with which the gripping surfaces of my clamp members (as illustrated in Fig. 13) are provided.

In the drawings, a main frame 1- has mounted thereon, a longitudinally. slidable crosshead 2 which is engaged by a screw 3 having. vabearing at e-and carrying a gear wheel 5. Gear wheel 5 is in mesh with a similar smaller gear 6 fixed upon a shaft carrying two sets of pulleys, one set being larger than the other and each setcomprising a tight pulley 7, 8, and a loose pulley according to the direction of its movement.

At the left (Figs. 1 and 2) is an auxiliary frame 11 which, as also main frame 1, must be fixedly attached. 'tothe floor. Pi otally attachedto frame 11, at 12, is a stretcher 13 comprising a frame 14 of angle iron, the inner endof: which, whenthis stretcher is in working position. rests. upon one end of the main framel (Fig. 2), while the outer end has attached weights 15 whereby, if the stretcher isswung into an upright position (dotted lines, Fig. 2) it. tends to remain in such position. r

The inner end of frame 14 is also provided with anattachedstrolley bracket .16 to which is fixed a short section of track 17.. Y

The. stretcher also. comprises a stretching plank 1.8'which normally rests'upon rollers 19 mounted in bearings fixed to the top of frame 14. Upon the upper side of this plank are mounted the two stretching clamps, the fixed clamp20. (Figs.'5 and 8) at the. outer end'of'theplank being tightly bolted thereto, and the remaining or loose clamp 21- (Figs. 6 and'7) being spaced from the fixed clamp and longitudinally, slidable with respect thereto.-

A draw rod 22'is bolted fast toeach end of cross head 2 and the free end of each rod is formed-as a hook 231, which lies against the outerside of the loose clamp 21 at its ends. 'Asthecross headis moved to the right (Figs. 1v and 2) by the screw 3, it will carnythe loose clamp with it. I

Each clamp comprises twohalvesor jaws, the upper j aws being alike both for the fixed andifor'theloose clamp. The loweriaw 24c-of the-fiX ed-gclamp;haslugs-25 which lie on each side of the stretcher plank and enable the clamp to be bolted fast thereto. The lower jaw 26of the loose clamp has similar lugs 25' whose extremities are bridged by a plate 27 so as to provide a slot by means of which the loose clamp is threaded over and made slidable u on the stretcher plank.

The ends of both clamps are provided with adjustable draw bolts 28 for bringing the jaws forcibly together when desired, said jaws tending to open up and separate from one another when the bolts are unscrewed byreason of the action of the springs 29' one of which is threaded over each bolt between the jaws.

The lower jaw 26 of the loose clamp also carries a pivotally attached pawl or dog 30 adapted to engage the teeth of a rack 31, which is fixed to the upper side of the stretcher plank 18, when the pawl is thrown downwardly, and to be free of said rack when the pawl is thrown upwardly.

Slots are milled out in the opposed portions of the jaws of both the fixed and the loose clamp. Each of these slots serves to receive an accurately fitted rib 32 formed, preferably integrally, on the back of an insert clamp bar 33 (Figs. 5, 6, 7, 8, 11, 12). This insert clamp bar is, preferably, of nickel-bronze made by the extrusion process as I find this material to be exceedingly hard and homogeneous when thus worked and, furthermore, to be inert chemically with respect to leather, organic materials generally found therein, and to the various oils, greases and other materials incorporated with the leather prior to the stretching operation. I

The body of each insert clamp bar is wider thanthe rib 32 and its inner face 34 is provided with a plurality of longitudinal flutes, these flutes being transverse to the stretching plank, therefore, when the clamp bar and clamp are in operative position (Figs. 1 to 8). The shape of theseflutes should be such that their intersection with a transverse plane will be defined by a smooth curve which will nowhere change its rate of curvature rapidly. In the particular embodiment used in the drawings I have employed a sinusoidal curve (Figs. 13 and 14) made up of smoothly joined identical circular arcs 35 and 36, which lie respectively below and above the axis of abscissae 3737, each arc subtending substantially an angle of 45. Instead of this particular curve I may use any simple sine curve if I desire. In this particular curve the height of the curve at its crest is substantially equal to one-fifth the length of the curve from crest to crest; I find these dimensions tobe satisfactory for use with all power belt stock including theheaviest.

with the adjacent portion lying below said axis.

It is also imperative that the rate of curvature of the flutes should be sufiicient to insure that leather pressed between the clamps should be securely held without, however, being great enough to stretch the fibers on the convex side of the leather or to compress fibers on the concave side of the leather, beyond their elastic limit.

I have found that the curve shown in Figs. 12- and 13, and previously described, will satisfy, for practically all power belt stock ordinarily used, the requirements just above specified;

The inner end of main frame -1 is provided with a notched block 38 and the inner end of the stretching plank, when in operative position, butts against the end of this block with the eye 39, which is bolted to the end of the stretching plank, lying in the notch.

A pulley 40, carrying a hanger from which is suspended a hanger link 41 engaged with eye 39, normally restswithin the trolley bracket 16 upon the track section 17 The stretching machine being in operative position, as shown in Fig. 1, a strip of leather to be stretched has its two ends placed between the fluted surfaces of the insert clamp bars of. the fixed and loose clamps respectively; the draw bolts 28 are then tightened so as to bring the upper and lower jaws together thus forcing the complementary surfaces of the opposed insert bars towardone another and compelling the leather to follow the shape or curve of the flutes. That is to say, the leather will be forced down into each concave groove by the corresponding convex rib of theopposed insert bar. be grippedby each pair of bars with a wedging action due to the fact that the'distance between the cooperating curves decreases at an increasing rate as the distance:

This will cause the leather to from the central points (the highest and a sufficient extent the shift lever 10 may be thrown so as to reverse the motion of screw 3 and cross head 2. Pawl .30 will prevent the loose clamp from slipping back and the leather will, therefore, remain in its condition of maximum stretch.

Hooks 23 will now be free of the loose clamp .so that the inner end of the stretcher may be thrown upwardly about itspivot 12 (as shown dotted in Fig; 1). In this position the track section 1 7 will fit into a gap of continuous trolley track (not shown) and the pulley with the suspended stretching plank and stretched leather thereonmay be run off to one side. From the other side a second stretching plank, similar to the first, may be run into place upon track section 17 and the stretcher again thrown down into operative position and a fresh pieceof leather put into place and stretched. And

so on indefinitely.

The leather may, of course, be removed from the stretching plank whenever desired by merely slacking the draw bolts 28.

When the leather'is thus gripped in my improved clamps as above described it is free from any discoloration.

held without the slightest slip and yet without the application of excessive strains to the draw bolts and clamps. There is, hence, no danger of breaking either bolts or clamps. And the leather, where it has been subjected to the gripping actionof the insert bars, while it will have been smoothly fluted in the pattern of the gripping surfaces of said bars, will have its surface unbroken and free from transverse lines of broken fibers such as are found when gripping surfaces comprising parallel teeth are employed Furthermore, these portions will be entirely They may, therefore, if suitably rolled out, be used on the under lap, where the leather stretched is alength of belting. And, except where the highest'finish is desired, they may be thus used on the top lap; And in any event, if these portions are not left on the belt or other article which has been stretched, they -may be out off and used for other suitable purposes and will command nearly as good a price as if they had never been subjected to the described pressure.

It shouldbe stated, furthermore, that the portions of leather which lie between the fluted clamping surfaces during the stretch? ing: operation are: themselves "as fully stretched as those free portions of the leather which lie between the fixed and loose '1 clamps.v Thisarises from: the fact that the leather is bent around and follows the curves of the interlocking flutes.

- Since the insert bars are inert to: the

greases and other materials which are squeezed out of the leather these materials will-hot be stained or discolored and, hence, when they spread to portions of. the leather adjacent to the clamps. such-portions will similarly remain unstained and free from 1. In a leather stretching machine, clamps the sections of whose opposed faces are compl'ementary sinusoidal curves, the height of which at the crests is substantially one-fifth the length of the curve from crest to crest, so that with respect to leather pressed between the'clamps the fibers thereof on the convex side will be stretched, while, conversely, the fibers on the concave side will be compressed but, in either case, not beyond their elastic limit. 2. In a leather stretching machine, clamp the sections of whose opposed faces are complementary sinusoidal curves, the height of which at the crest is so proportioned to the length of the curve from crest to crest that, with respect to leather pressed between the clamps, the fibers thereof on the convex side will be stretched while, conversely, the fibers on the concave side will be compressed but, in either case, not beyond their elastic limit. 3. In a leather stretching machine, clamps whose opposed faces are provided with a plurality of smooth flutes, the shape of each fluted surface being such that its intersection with a transverse plane is a curve whose adjacent portions merge smoothly into one another and are alternately convex and concave, the faces being, further, complementary to one another-and the dimensions of the curves being such that, with respect to leather pressed between the clamps, the fibers thereof on the convex side will be stretched while, conversely, the fibers on the concave side will be compressed but, in

serve as gripping faces, the rate of curvature of the flutes being such that leather pressed between the clamps will be held without permanent deformation.

5. In a leather stretching machine, clamp bars having a plurality of opposed fluted and complementary faces of nickel-bronze, the rate of curvature of the flutes being such that, with respect to leather pressed between the clamps, the fibers thereof on the convex side will be stretched but not beyond their elastic limit while the fibers on the concave side will be compressed but not beyond their elastic limit.

6. In a leather stretching machine, elonfive cents each,

gated clamps of nickel-bronze having axially disposed complementary flutes whose sections are sinusoidal curves, the rate of curvature of which is such that leather pressed between the faces, while it will be bent to conform with the shape of said faces will nowhere be bent sufficiently to deform the fibers beyond their elastic limit.

In testimony whereof I have hereunto subscribed my name.

PHILIP CARTER BROWN.

Witnesses:

MELVIN A. GALRICIA, HARRY C. GLIDDEN.

by addressing the Commissioner of Patents,

Washington, D. G. 

